JP5160211B2 - Synchronous rectifier converter - Google Patents

Description

  The present invention relates to a synchronous rectification converter for parallel redundant operation.

  A conventional synchronous rectification converter for parallel redundant operation has a diode or power MOSFET for redundant operation. For example, when the voltage of another converter connected in parallel rises, the synchronous rectification converter performs the output voltage stabilization operation. As a result of the operation of lowering the output voltage, the regenerative current flows from the secondary side to the primary side of the synchronous rectifier converter, and as a result, excessive voltage and current stress may occur in the switching element and the rectifier switch.

In order to solve this problem, a synchronous rectifier converter having a means for detecting the direction of the current flowing in the primary or secondary side and suppressing the occurrence of stress by turning off the rectifier switch when the regenerative current starts to flow is invented. (See Patent Documents 1 and 2).
JP-A-6-343262 JP 2004-336908 A

  According to the invention, it is possible to suppress the occurrence of excessive voltage and current stress in the switching element and the rectifier switch. However, these synchronous rectifier converters need to include a current detection circuit such as a resistor and an amplifier for amplifying the detection signal. As a result, there is a problem that the detection circuit becomes complicated.

  The present invention has been made in view of the above problems, and provides a synchronous rectification converter for parallel redundant operation that can easily detect a regenerative current with a small number of parts.

  In order to solve the above problems, a synchronous rectifier converter according to the present invention has a primary and secondary insulated by a transformer, and a secondary side is provided with a rectifying switch and a smoothing circuit synchronized with a primary main switch. A synchronous rectifier converter, comprising a redundant switch on the output side of the secondary side, and regenerative current detecting means for detecting a potential difference between input and output when the voltage on the input side of the redundant switch is lower than the output side. A control circuit is connected to the output terminal of the regenerative current detection means and the control terminal of the rectifier switch, and the control circuit detects the regenerative current by the regenerative current detection means, and the two rectifier switches The control signal is configured to be stopped.

The synchronous rectifier converter according to the present invention is characterized in that the rectifier switch is constituted by a MOSFET.
The synchronous rectifier converter according to the present invention is characterized in that the redundancy switch is constituted by a MOSFET.

  In the synchronous rectifier converter according to the present invention, the regenerative current detecting means includes a switch on the output side of the secondary side, the switch detects a potential difference between the input and output of the redundant switch, and It is characterized in that it is determined that a regenerative current has flowed when the voltage on the input side of the redundant switch is lower than the output side.

  According to the present invention, a redundant switch is provided on the output side of the secondary side, and the regenerative current detecting means is provided so as to detect the potential difference between the input and output when the voltage on the input side of the redundant switch decreases from the output side. Thus, there is an effect that the regenerative current can be detected more easily and with a smaller number of parts than in the past without directly monitoring the regenerative current.

  A circuit diagram of the best mode for carrying out the invention is shown in FIG. The synchronous rectification converter shown in FIG. 1 is a forward converter. In this synchronous rectification converter, the primary and secondary are insulated by a transformer T1. The primary side is provided with a main switch Q1 composed of a DC input source and a MOSFET. The insulated secondary side is provided with two rectifying switches Q2 and Q3 constituted by MOSFETs, and these switches Q1, Q2 and Q3 are configured to operate in synchronization. In the present embodiment, a smoothing circuit is constituted by the output choke L1 and the smoothing capacitor C1 on the secondary side. Further, on the output side of the smoothing circuits L1 and C1, a redundancy switch circuit 3 having a redundancy switch Q4 formed of a MOSFET is provided. A regenerative current detection circuit 1 for detecting a potential difference between input and output when the voltage on the input side of the redundancy switch Q4 drops from the output side is provided at both ends of the redundancy switch circuit 3.

  The regenerative current detection circuit 1 includes a switch Q5. The switch Q5 is composed of a transistor. The base and emitter of the switch Q5 are connected to the input / output terminal of the redundancy switch circuit 3, and the collector of the switch Q5 is connected to the control circuit 2. Thus, the potential difference between the input and output of the redundancy switch circuit 3 is detected, and it is determined that the regenerative current has flowed when the voltage on the input side of the redundancy switch circuit 3 drops from the output side.

  The control circuit 2 is connected to the gate terminals of the switches Q1 to Q3. In particular, by connecting the gate terminals of the two rectifying switches Q2 and Q3 to the control circuit 2, when the regenerative current detecting circuit 1 detects the regenerative current, the control signals of the two rectifying switches Q2 and Q3 are stopped. It is constituted as follows.

  As shown in FIG. 3, the control circuit 2 comprises drive circuits 21, 22, and 23, an output stabilization control PWM signal source 5, a comparator M21, a reference power supply VREF21, logic gates M2-A, M2-B, and the like. When a regenerative current detection signal is input from Q5, it functions to stop the control signals of the rectifying switch Q2 and the commutation switch Q3 as shown in FIG. Output stabilization control PWM signal source 5 detects the output voltage and generates a pulse train that is width-modulated so that the output voltage is stabilized to a preset voltage and that is adapted to each connected switch. To function.

  The redundancy switch circuit 3 is composed of a switch element Q4, a resistor R1 for detecting a current flowing through the switch, and a control circuit 4. The control circuit 4 reverses the switch Q4 based on a detection voltage at both ends of the resistor R1. It functions to switch the switch Q4 from on to off when it is about to flow.

  Further, the synchronous rectifier converter according to the present invention constitutes a redundant power supply system as a whole by being connected to one or more similar power supplies via such a redundant switch.

  The synchronous rectifier converter configured as described above operates as follows. First, in the normal state, since the operation is almost the same as that of many conventional synchronous rectifier converters, the description is omitted.

  Next, a case where a regenerative current flows when the voltage of another converter connected in parallel rises based on FIG. 4 will be described. 4A shows the output voltage Vout of the converter, FIG. 4B shows the output current Iout of the converter flowing in the redundancy switch circuit 3, FIG. 4C shows the voltage VC1 across the output capacitor, and FIG. 4D shows the regenerative current detection. The output voltage VQ5out of the switch Q5 provided in the circuit 1, (e) is the output voltage VM21 of the comparator M21, (f) is the output pulse VPWMout of the output stabilization control PWM signal source 5, and (g) is the output of the drive circuit 22. Pulse V22. When the voltage Vout of the converter increases, the converter output current Iout decreases, and a reverse current that flows into the converter via the redundancy switch Q4 tends to flow.

  The redundancy switch Q4 is switched from on to off by the action of the control circuit 4 of the redundancy switch that prevents current from flowing in the reverse direction from the load side to the power source side, and the reverse current is blocked.

  When the regenerative current continues to flow due to the stabilization operation of the output stabilization control PWM signal source 5, the output capacitor C1 is discharged and the voltage VC1 of C1 decreases. As a result, a potential difference is generated between the input and output of the redundancy switch circuit 3, and the voltage on the input side of the redundancy switch circuit 3 decreases from the output side. That is, the emitter terminal of the switch Q5 provided in the regenerative current detection circuit 1 is at a high level, while the base terminal of the switch Q5 is at a low level, and the switch Q5 is turned on. When the switch Q5 is turned on, the output voltage VQ5out of the switch Q5 becomes high level. As a result, the output VM21 of the comparator M21 of the control circuit 2 is inverted to the negative side, and the output is stabilized by the function of the logic gates M2-A and M2-B. The output pulse VPWMout of the control PWM signal source 5 is blocked from being transmitted to the drive circuits 22 and 23, and the two rectifier switches Q2 and Q3 are turned off as indicated by V22 in FIG. As a result, the regenerative current is prevented from flowing from the secondary side to the primary side of the synchronous rectifier converter, and excessive voltage and current stress generated in the main switch Q1 and the rectifier switches Q2 and Q3 can be suppressed.

  Next, FIG. 2 shows an embodiment different from the synchronous rectifier converter shown in FIG. The synchronous rectification converter shown in FIG. 2 is a half-bridge converter. In this synchronous rectification converter, the primary and secondary are insulated by a transformer T1. The primary side is provided with two main switches Q11 and Q12 formed of a DC input source, input capacitors C11 and C22 constituting a bridge circuit, and a MOSFET.

  The insulated secondary side is provided with two synchronous rectification switches Q2 and Q3 constituted by MOSFETs. In the present embodiment, a smoothing circuit is constituted by the output choke L1 and the smoothing capacitor C1 on the secondary side. Further, a redundancy switch circuit 3 composed of a MOSFET is provided on the output side of the smoothing circuits L1 and C1. By detecting a regenerative current on the output side of the redundant switch circuit 3, a regenerative current detection circuit 1 is provided for detecting a potential difference between input and output when the voltage on the input side is lower than that on the output side. The regenerative current detection circuit 1 is the same as the embodiment shown in FIG.

  The control circuit 2 is connected to the gate terminals of the switches Q3, Q4, Q11, and Q12. In particular, by connecting the gate terminals of the switches Q2 and Q3 to the control circuit 2, when the regenerative current detection circuit 1 detects the regenerative current, the control signals of the rectifying switches Q2 and Q3 are stopped. is there.

  The synchronous rectifier converter of the embodiment shown in FIG. 2 is configured as described above. Next, the operation will be described. In the normal state, the operation is almost the same as that of many conventional synchronous rectifier converters, and thus the description thereof is omitted. Subsequently, a case where a regenerative current flows will be described. In this case, a potential difference is generated between the input and output of the redundancy switch circuit 3, and the voltage on the input side of the redundancy switch circuit 3 is lower than that on the output side. That is, the emitter terminal of the switch Q5 provided in the regenerative current detection circuit 1 is at a high level, whereas the base terminal of the switch Q5 is at a low level and the switch Q5 is turned on. When the switch Q5 is turned on, a signal is output to the control circuit 2, and the two synchronous rectification switches Q2 and Q3 are turned off by the operation of the control circuit 2 similar to that in the above embodiment. Thereby, it is possible to prevent the regenerative current from flowing from the secondary side to the primary side of the synchronous rectifier converter, and to suppress excessive voltage and current stress generated in the switching element and the rectifier switch.

  In this embodiment, the forward converter and the half-bridge converter are taken up. However, the present invention can be applied to any synchronous rectifier converter as long as it is an insulating synchronous rectifier converter having a switching element on the secondary side.

  According to the present invention, a redundant switch is provided on the output side of the secondary side, and the regenerative current detecting means is provided so as to detect the potential difference between the input and output when the voltage on the input side of the redundant switch decreases from the output side. Thus, the regenerative current can be detected industrially without the need to directly monitor the regenerative current, and the regenerative current can be detected more easily and with fewer parts.

1 is a circuit diagram of the best mode for carrying out the invention in a synchronous rectifier converter according to the present invention; FIG. FIG. 2 is a circuit configuration diagram of an embodiment different from the embodiment shown in FIG. 1. It is a circuit block diagram about the principal part of the synchronous rectification converter based on this invention in the said Example. It is an operation | movement waveform diagram in the said Example.

Explanation of symbols

Regenerative current detection circuit
2 Control circuit 3 Redundant switch circuit 4 Redundant switch control circuit Q1, Q11, Q12 Main switch Q2, Q3 Secondary side synchronous rectifier switch Q4 Redundant switch Q5 Regenerative current detection switch T1 Transformer L1 Output choke
C1 Smoothing capacitor C11, C12 Input capacitor

Claims (4)

A synchronous rectifier converter in which a primary and secondary are insulated by a transformer and a rectifier switch and a smoothing circuit synchronized with the secondary side are provided,
The secondary output side is provided with a redundancy switch, and is provided with regenerative current detection means for detecting a potential difference between input and output when the voltage on the input side of the redundancy switch is lower than the output side. A control circuit is connected to the output terminal of the detecting means and the control terminal of the rectifying switch, and the control circuit is configured to stop the control signal of the rectifying switch when the regenerative current detecting means detects the regenerative current. A synchronous rectifier converter characterized by the above. 2. The synchronous rectifier converter according to claim 1, wherein the rectifier switch is constituted by a MOSFET. 3. The synchronous rectifier converter according to claim 1, wherein the redundancy switch is constituted by a MOSFET. The regenerative current detection means includes a switch on the output side of the secondary side, the switch detects a potential difference between the input and output of the redundancy switch, and the voltage on the input side of the redundancy switch is output side 4. The synchronous rectifier converter according to claim 1, wherein when it is further lowered, it is determined that a regenerative current has flowed.

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